WBJEE 2020 Math Solved Paper

(

x

y

)2+2(

x

y

)+a=0 & a(

x

y

)2+2(

x

y

)+1=0 have exactly one root in common (taking

x

y

as a single variable).
By, (a1b2−a2b1)(b1c2−b2c1) =(a1c2−a2c1)2
We get : ⇒ a = 1 or –3
a cannot be 1
Taking a = –3, roots of 1st equation : 1, –3 and 2nd equation : 1,−

1

3

So other lines :

x

y

=−3 and

x

y

=−

1

3